Hello. I need to create a button of the triangular form. I have made such panel with button:

PANEL* m_pan =
{bmap = "panel.pcx";
button (10, 80, "btn_On.pcx", "btn_of.pcx", "btn_over.pcx", On_Click, NULL, NULL);
flags = OVERLAY | VISIBLE;}

I created a button texture. The texture is rectangle. The area out of a triangle which should not be visible I has made black. The button correctly is displayed in program. But the button reacts not only to pressing mouse in a triangle, but also round a triangle, within all texture of the button (visible+invisible part of button texture). Is it possible to make so the button would react only on mouse click in a visible part?

from manual: "Free-form buttons can be used when the button function retrieves the pixel at the mouse position through pixel_for_bmap(), and uses the pixel color or alpha value to determine whether the button was hit or not."

under panel->panel elements->buttons - remarks